Naked Dance of Terror: Mumbai Serial Blasts (Latest Photos)

Investigators probing on Wednesday's bomb blasts in Mumbai which killed at least 17 and injured 131 are zeroing in on the likely involvement of the Indian Mujahideen, a domestic terrorist group.

Police confirmed the explosive devices used were crude home-made bombs hidden in traditional steel lunch-boxes and were left in public places, which they say is a trademark of group responsible for several other attacks in various Indian cities in recent years.

In February last year, the Indian Mujahideen (IM) were responsible for an attack in the western city of Pune and in 2008, they also struck in Delhi.

Investigators say they believe the group intends to strike on the 13th or 26th of the month, a pattern that dates back to 13 May 2008 when the group targeted Jaipur.

However, despite the investigators' suspicions, so far nobody has claimed responsibility for the attacks, which also left at least 131 injured.

A plain-clothed policeman surveys the aftermath at the site of an explosion near the Opera House in MumbaiReuters

A man injured by an explosion is assisted after arriving to a hospital in MumbaiReuters

A man, injured by an explosion on Wednesday, is moved through the halls of a hospital to be treated for his burns in MumbaiReuters

A policeman kept guard in the rain at the site of an explosion near the Opera House in MumbaiReuters

Policemen stand guard in rain next to barricade they installed at one of sites of Wednesday's triple explosions, near Opera House in MumbaiReuters

India's FM Krishna speaks to the media as former Afghan President Rabbani listens in New DelhiReuters

Policemen surround a vehicle which was damaged at the site of a bomb explosion in the Dadar area of MumbaiReuters